It would be great if there was a generic must function in "builtin" package.

It would be equivalent to this:

eg. 
Say we have an arbitrary function that looks like this:
x, y, z, err := function()

x, y, z is of arbitrary type T1, T2, T3 respectively.

the proposed must( function() ) function will return x of type T1 if err == nil and panic(err) if err != nil

The function is better suited for functions which return 2 values, the last of which is type error. But it can be generalized to any number of return values provided the final return value is of type error.